(1) Field of the Invention
The present invention relates to a storage system, and more particularly to a storage system which allows a plurality of clients involved in any network to share file data if the storage system is connected to the network.
(2) Description of Related Art
As a conventional scheme of operating a network in which file data is shared by a plurality of nodes (clients) (hereinafter simply referred to as file sharing), there can be introduced a well-known manner in which, as for example schematically shown in FIG. 16, a file server 200 is built in any network 100 such as a LAN (Local Area Network) by utilizing an NFS (Network File System), and the file server 200 is connected with a secondary storage unit 400 through an interface 300 such as a so-called SCSI (Small Computer System Interface), and the file is shared by a plurality of clients 500 through the secondary storage unit 400.
The above-introduced manner, however, can encounter the following problems.
(1) Highly developed skill is requested for a person who is under duty of building the file server system and maintaining the same.
(2) It is not easy to expand the file server system (in its capacity, accessing performance or the like). If the system can be apparently expanded, one file server is unavoidably divided into a plurality of units and the entire number of units constituting the system becomes large, with the result that the maintenance cost for the system is also increased.
(3) Also, highly developed skill is requested for a person who is under duty of building the file server system and maintaining the same when the system suffers from any failure. Accordingly, the cost therefor will be expensive.
As a method for solving the problems, recently, there are proposed a method known as an NAS (Network Attached Storage). The NAS is equivalent to a unitarily built storage system including the file server 200 and the secondary storage unit 400 (see the portion surrounded by broken line in FIG. 16). If the NAS is connected to the network and simple setting operation is executed, the clients involved in the network can share data file, and further highly developed skill is unnecessary for a person under the duty of building the system and maintaining the same.
However, the above-described NAS still encounters a problem that it does not have satisfactory scalability for coping with the expansion of the transmission rate (in the current status, the transmission rate is of about 1 Gbps, which is expected to reach about 10 Gbps in several years in the future) of an LAN which is now progressively deployed. In other words, if the communication system is arranged so as to deal with the network as a connection destination which is increasing in the transmission rate, it is unavoidably required to increase the number of file servers and secondary storage units provided within the NAS. As a result, a component which functions as the file server is divided into a plurality of components, and a component which functions as the secondary storage unit managed by the file server is also divided into a plurality of components.
That is, the above file server 200 and the secondary storage unit 400 are arranged as processing channels functioning in a parallel manner (independent manner). For this reason, it becomes necessary to carry out maintenance on each of the file server components, with the result that the maintenance cost will be increased.